Amphiphilic block copolymer and method for preparing same

Abstract

The invention relates to an amphiphilic block copolymer, to the preparation thereof, and to the use thereof in the form of a self-stabilizing latex. The copolymer has the formula R 5 O—[—CH 2 CH 2 —O—] n —C(═O)—CR 3 R 4 —[CH 2 CR 6 R 7 ] m —S—C(═S)—S—R 1 where: R 1 is a straight or branched alkyl group, an alkenyl group having one or more —C═C— bonds, or an alkynyl group having one or more —C≡C— bonds, said groups including 8 to 18 carbon atoms; 20≦n≦100; R 3 and R 4 each are independently H, an alkyl group with 1 to 4 carbon atoms, or a nitrile group, at least one of R 3 and R 4 being different than H; R 6 is a phenyl group or an alkoxycarbonyl group in which the alkoxy group includes 1 to 8 carbon atoms; R 7 is a hydrogen atom or a methyl radical; and 20≦m≦1000. The preparation method comprises: preparing an aqueous solution of a compound R 1 —S—C(═S)—S—CR 3 R 4 —C(═O)—OR 2 in which R 2 is R 5 —[—O—CH 2 CH 2 —] n —, R 5 being a hydrophilic group and 20≦n≦100; adding to said solution one or more hydrophobic monomers of the formula (II) R 6 —CR 7 ═CH 2 and a free radical polymerization initiator; and heating said aqueous solution to a temperature of 60-90° C.

The invention claimed is: 
     
       1. A method for preparing an amphiphilic copolymer, in emulsion in an aqueous medium, said method consisting of:
 preparing an aqueous solution of a compound of formula (I) below:
   R 1 —S—C(═S)—S—CR 3 R 4 —C(═O)—OR 2   (I)
 
 
 
       in which:
 R 1  represents a linear or branched alkyl group, an alkenyl group having one or more —C═C— bonds, or an alkynyl group having one or more —C≡C— bonds, said groups having from 8 to 18 carbon atoms; 
 R 2  represents an R 5 —[—CH 2 CH 2 —] n — group in which R 5  is a hydrophilic group and 20≦n≦150; 
 R 3  and R 4  each represent, independently of one another, H, an alkyl group having from 1 to 4 carbon atoms or a nitrile group, at least one among R 3  and R 4  being other than H; said aqueous solution being free of free surfactant, 
 successively adding to said solution one or more hydrophobic monomers of formula (II) below:
   R 6 —CR 7 ═CH 2   (II)
 
 
 
       in which:
 R 6  represents a phenyl group or an alkoxycarbonyl group in which the alkoxy group has from 1 to 8 carbon atoms and optionally bearing one or more functional groups, and 
 R 7  represents a hydrogen atom or a methyl radical, 
 
       then a free-radical polymerization initiator; and then
 in bringing said aqueous solution to a temperature of 5-95° C. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the hydrophilic group R 5  of the compound of formula (I) is H a —(CH 2 ) p —CH 2 —R 8  group in which p is 0 or 1, and R 8  represents H or a group chosen from —COOM, —SO 3 M, —OSO 3 M, —N(CH 3 ) 2  and —N(CH 3 ) 3   + X − , M being H or an alkali metal, X being Cl, Br or I. 
     
     
       3. The method as claimed in  claim 1 , wherein the hydrophobic monomer/compound I molar ratio is between 20 and 1000.